<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<script src="../vue.js"></script>

<body>
  <div id="app">
    <p>我是根标签结构</p>
  </div>


  <script>
    var vm = new Vue({
      el: "#app",
    })
    vm.$el.innerHTML = "<h1>我是替换后的根标签结构</h1>"
  </script>
</body>

</html>